feat: implement automatic message delivery acknowledgement to trigger real-time double-tick status updates

lib/features/messaging/data/socket_service.dart

@@ -139,6 +139,13 @@ class SocketService {
     _socket!.on('new_message', (data) {
       try {
         final message = ChatMessage.fromJson(data as Map<String, dynamic>);
+        // Auto-ack delivery so sender gets real-time double-tick
+        try {
+          _socket?.emit('message_received', {
+            'messageId': message.id,
+            'conversationId': message.conversationId,
+          });
+        } catch (_) {}
         _messageController.add(message);
       } catch (e) {
         _log.e('Error parsing new_message: $e');
@@ -305,6 +312,16 @@ class SocketService {
     _socket?.emit('mark_read', {'conversationId': conversationId});
   }
 
+  /// Acknowledge that we (the receiver) have received a message via socket.
+  /// Backend marks it as DELIVERED and emits `message_delivered` to the sender,
+  /// making the sender's tick update from single → double in real time.
+  void ackMessageReceived(String conversationId, String messageId) {
+    _socket?.emit('message_received', {
+      'conversationId': conversationId,
+      'messageId': messageId,
+    });
+  }
+
   void dispose() {
     disconnect();
     _messageController.close();

lib/features/messaging/presentation/providers/messaging_provider.dart

@@ -106,6 +106,10 @@ class MessagingNotifier extends StateNotifier<MessagingState> {
       final isMine = message.senderId == _currentUserId;
       if (isMine) return;
 
+      // Immediately ack delivery to backend so sender's tick goes single → double.
+      // This works regardless of Redis presence state and avoids races on send.
+      _socket.ackMessageReceived(convId, message.id);
+
       currentMessages.insert(0, message);
       final updatedMessages =
           Map<String, List<ChatMessage>>.from(state.messages)